1. Field of the Invention
The present invention relates to a vehicle diagnosing apparatus which diagnoses a vehicle via an electronic control unit (ECU) mounted on the vehicle by using a portable diagnosing unit which is connected to the electronic control unit.
2. Description of the Related Art
As this kind of vehicle diagnosing apparatus, there has hitherto been known, in the Published Unexamined Japanese Patent Application No. 15095/1996, an apparatus comprising a host computer which wirelessly communicates with a portable diagnosing unit. The data obtained as a result of diagnosing (hereinafter called diagnosing data) of the vehicle are transmitted to the host computer to thereby perform such a processing of the data as the totalization, control, etc.
In the diagnosing apparatus of this prior art, diagnosing programs which have been prepared exclusively to suit each kind (or type) of electronic control unit are contained inside different read-only memory (ROM) cartridges. Each of the ROM cartridges is detachably mounted on the portable diagnosing unit. When the kind of the electronic control unit is changed, the ROM cartridge is replaced to another one to cope with the change in the kind of the electronic control unit.
Further, in Published Examined Japanese Patent Application No. 76724/1995, there is known the following. Namely, diagnosing programs which have been prepared exclusively to suit each kind of portable diagnosing unit are all contained in a memory portion (or a memory module) of the portable diagnosing unit. When the portable diagnosing unit is connected to the electronic control unit, the data on the kind of the electric control unit are read out to thereby call up a diagnosing program which corresponds to the data on the kind of the electronic control unit.
If the diagnosing programs are all contained in the memory portion of the portable diagnosing unit as in the above-described latter example of the conventional art, a large capacity is required in the memory portion. As a result, the portable diagnosing unit becomes large in size and the ease with which the portable diagnosing unit can be carried is impaired.
On the other hand, if the ROM cartridges are used as in the former example of the conventional art, a large memory is not required. However, with the increase in the number of kinds of the electronic control units, the number of the ROM cartridges correspondingly increases. As a result, their control becomes troublesome and the selection of the ROM cartridges must be done by the operator himself. There is, therefore, a possibility that the wrong ROM cartridge is selected, resulting in a failure in diagnosing.
In view of the above-described points, the present invention has an object of providing a vehicle diagnosing apparatus which can cope with the change in kind of the electronic control unit without using ROM cartridges and without impairing the ease with which the portable diagnosing unit can be carried.